Nesting Box????

Once again we have blue Tits in our cigarette end box, this is the forth year running, I have had a sneak look and there are eggs and the mother is sitting on them, I can hear her coughing from where I'm blipping this, as she must be up to 40 a day by now.
Here is the male bringing what looks like a petal from a buttercup, probably to sweeten the smell in there.
We will put a notice on it to prevent anyone sticking in a lighted cigarette end, as we do have a large meeting there tomorrow, anyway I will make them aware not to extinguish their cigarettes there.